The present invention relates to a vibration actuator which is mainly mounted on mobile communication apparatuses such as a cellular phone, and which has a function of generating a call sound, a voice, and a vibration.
A conventional vibration actuator is disclosed in FIG. 5 of U.S. Pat. No. 5,528,697 issued to Yoshikazu Sato. The conventional vibration actuator comprises a magnet, a pole piece, and a yoke which are coupled with one another to form a magnetic circuit device with a magnetic gap. The magnetic circuit device is elastically suspended to a case or a vibration transmitter by a spring body or a suspension plate in a predetermined direction. A diaphragm is attached as a vibrating member to the case. A coil is fixed to the diaphragm and disposed in the magnetic gap of the magnetic circuit. In the conventional vibration actuator, the magnetic circuit device is directly suspended by only the suspension plate to the vibration transmitter. With this structure, a Q (indicating hereinunder the steepness in mechanical resonance) is great during vibration resonance to narrow a band of the vibration. As a result of narrowing the band, a large resonance positional deviation occurs dependent on use conditions. Accordingly, it is necessary to use a complicated circuit in order to drive the conventional vibration actuator.